Secure multi database system including a client, multi database server, and database server

ABSTRACT

A definition tool of the present invention declares columns which are concealed in external tables to a multi-database server. The multi-database server controls a decomposition and an execution of query messages such that the multi-database server does not perform an arithmetic using the concealed columns. The external database server encrypts the data of concealed columns in tables of query result tables. The multi-database server designates a range to be decrypted at the time of acquiring and integrating respective result tables. A client program acquires an integrated result table and decrypts the designated range. Since the data encrypted by the external database server is decrypted by and is referred to the client program, it becomes difficult for the multi-database server to refer to a content of the concealed columns.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multi-database system where databasesare present in a distributed form. Among others, the present inventionrelates to security for the disclosure of information of themulti-database system. The present invention, more particularly, relatesto a secure multi-database system in which a plurality of databases areoperated in an federating manner and security for individual databasesis ensured, and an information mediation system on a network to whichsuch a system is applied.

2. Description of the Related Art

Currently, as a technique for getting access to a multi-database (MDB)system, there has been known a technique which gets access to a table(an external table) of an external database (external DB) through anexternal data wrapper. In this technique, a user declares an accessmethod to the external DB or the configuration of the external table tothe MDB system. In the MDB system, the external table is handled in thesame manner as a usual view table and it is possible for the user todeclare a view table which combines external tables together or a viewtable which combines the external table with a table inside the MDBsystem (an internal table).

ISO/IEC standardizes the architecture and a database language of thisMDB system as “Database Language SQL-Part 9: Management of External Data(SQL/MED)” which is a database language SQL having a specification Part9 for a next generation known as SQL3 or SQL-Part 99. With respect toSQL/MED, a draft of ISO/IEC is laid open to the public and as an articlewhich interprets ISO/IEC, ACM SIGMOD Record, Vol.29, No.1, March 2000,pp63-67, “SQL Standardization: The Next Steps” is available.

Conventionally, as security for DB, a method which sets an accessauthority to the data to individual users and controls access to the DBbased on such access authority “access control” has been dominantlyused. The same goes for the MDB.

Recently, along with the popularization of the Internet, the Intranetand the Extranet, the chances that the user gets access to the DBthrough the network have been increased. In this case, to protect thequery messages and data being transmitted through the network fromimproper access, there has been proposed a method which transmits thequery messages and data after encrypting the query messages and data. Asa method for encrypting the query messages, U.S. Pat. No. 5,713,018discloses “SYSTEM AND METHOD FOR PROVIDING SAFE SQL-LEVEL ACCESS TO ADATABASE”. Further, as a method for processing data by encrypting thedata on a DBMS, U.S. Pat. No. 5,963,642 discloses “METHOD AND APPARATUSFOR SECURE STORAGE OF DATA”.

Further, as an example which adopts a multi-database system as aninformation mediation business on the Internet, “Yodlee.com” is known.This business is a service which provides the service details whichindividual service providers provide in a form that the service detailsare integrated into one. The user can get the reference of all of theservice details by merely getting access to Yodlee.com and hence, it isunnecessary for the user to get access to individual service providers.Yodlee.com regards individual service providers as information sourcesand performs inquiries of the service details to the service providerswhile setting respective users as keys and integrates and provides theresults of inquiries to the users. Here, although the acquired servicedetails are cached in an internal DB, security is ensured by encryptingthe data of this internal DB.

SUMMARY

First of all, problems on techniques to realize the informationmediation business on a network which are analyzed by inventors of thepresent invention are explained in conjunction with FIG. 17. Then,taking this business as an example, tasks to be solved by the presentinvention are specifically explained.

The information mediation business is a service business which virtuallyintegrates information sources distributed on the network and providesan integrated access path to users. When viewed from the stand point ofusers, since destinations to which inquiries are made are integratedinto one, the availability is increased. The previously mentionedYodlee.com is also a kind of information mediation business andintermediates enterprises and personal users. This mode is a so-called“B2C type”. Besides this B2C type, there exists a mode of B2B type whichintermediates enterprises and enterprise users and FIG. 17 shows such anexample.

In FIG. 17, a mediator 301 provides an access path for an A salescompany 304 a, a B sales company 304 b and a C sales company 304 c to anaaa company 303 a, a bbb company 303 b and a ccc company 303 c whichconstitute client enterprises as virtual detailed statement slips 302a-302 c. The substance of the virtual detailed statement slips is a viewtable and respectively declares transaction information 45 a, 45 b and45 c as external tables in a multi-database server 1 and merges themusing respective client enterprises as keys. Inquiries from clients 3 a,3 b and 3 c are transmitted to respective DB 45 a-45 c through themulti-database server 1 and tables on query results (result tables) areintegrated and returned to respective clients. In this specification,“declaration” or “to declare” means “to designate”.

With respect to this business, in the multi-database server 1, a systemto ensure the security for virtual detailed statement slips of clientsbecomes far more important than a conventional case. This is becausethat to consider the business from a viewpoint of security, although thetransaction information is distributed to the database of respectivesales companies so that the risk brought about by improper accessbecomes inevitably distributed, since the transaction information aremerged through virtual detailed statement slips so that damages when theimproper access happens are increased. Particularly, if it is possibleto provide a system in which even if the mediator 301 is anadministrator of the multi-database server 1, he cannot observe thecontents of the mediation information so that the reliability of themediator from not only the users but also the information provider sidecan be increased.

Subsequently, tasks of conventional techniques to satisfy this requisiteare explained.

First of all, in an access control, although an unauthorized user isprevented from getting access to the virtual detailed statement slips,the administrator can easily get access to the virtual detailedstatement slips and hence, the above-mentioned requisite cannot besatisfied. Eventually, it is difficult for the mediator to acquire thereliability from the users and the information providers so that it isdifficult to establish the information mediation business.

Although the method which encrypts query messages and result tableswhich are transmitted through the network can prevent these informationfrom being improperly stolen or forged, the method is only applicable toa case where a client and a database correspond to each other on a oneto one basis. That is, there has been a problem that it is difficult todirectly apply this method to a multi-database.

Although the previously mentioned Yodlee.com method encrypts data to bestored in an inner DB so that it provides a system in which even anadministrator can not easily refer to data of the inner DB, theadministrator can refer to data before the data is encrypted in amulti-database server in principle so that it is difficult to completelysatisfy the above-mentioned requisite. Further, a man who sets andexecutes the encryption is the administrator himself so that it isdifficult for users and information providers to totally rely on themediator.

Accordingly, it is a first object of the present invention to provide asecure multi-database system in which it is difficult even for anadministrator to observe contents of data transacted between clients andexternal database.

Further, it is a second object of the present invention to provide ainformation mediation system in which it is difficult even for anadministrator to observe contents of information transacted betweenusers and information providers.

To achieve the above-mentioned objects, the present invention adoptsfollowing configurations.

In a multi-database system of the present invention, a plurality ofdatabase apparatuses which respectively store data, a multi-databaseprocessing apparatus which performs an integration processing of datastored in a plurality of the above-mentioned database apparatuses anduser processing apparatuses which receive data subjected to theintegration processing from the multi-database processing apparatus areconstituted such that they are connected each other through a network.

Among the distributed data which are necessary for the above-mentionedmulti-database processing apparatus to perform the integrationprocessing, a plurality of database apparatuses respectively perform theconversion processing based on a predetermined rule with respect topartial data in a give data region contained in the distributed data andtransmit the distributed data containing the partial data which aresubjected to the conversion processing to the above-mentionedmulti-database processing apparatus.

Further, the above-mentioned multi-database processing apparatusreceives a plurality of the distributed data containing the partial datawhich are subjected to the conversion processing from a plurality ofdatabase devices, and generates the integral data by integrating aplurality of received distributed data, and transmits the integrateddata to the user apparatuses.

In the above-mentioned conversion processing, it may be possible toperform the conversion such that the converted partial data is notdisclosed. For example, the conversion processing includes theapplication of encrypting processing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view expressing a software configuration of asecure multi-database system according to one embodiment of the presentinvention.

FIG. 2 is an explanatory view showing a hardware configuration of asecure multi-database system according to one embodiment of the presentinvention.

FIG. 3 is an explanatory view showing a use example of securemulti-database system according to one embodiment of the presentinvention.

FIG. 4 is an explanatory view showing an example of definition messagesof an external table in a secure multi-database system according to oneembodiment of the present invention.

FIG. 5 is an explanatory view showing an example of definition messagesof a view table in a secure multi-database system according to oneembodiment of the present invention.

FIG. 6 is an explanatory view showing a processing flow of querymessages in a secure multi-database system according to one embodimentof the present invention employing a use example.

FIG. 7 is an explanatory view showing a processing flow of result tablesin a secure multi-database system according to one embodiment of thepresent invention employing a use example.

FIG. 8 is an explanatory view showing an external table definitioninformation in a secure multi-database system according to oneembodiment of the present invention employing a use example.

FIG. 9 is an explanatory view showing a flow of an MDB definitionregistration processing in a secure multi-database system according toone embodiment of the present invention.

FIG. 10 is an explanatory view showing a flow of a meaning checkprocessing with designation of inquiries in conjunction with concealmentcolumns in a secure multi-database system according to one embodiment ofthe present invention.

FIG. 11 is an explanatory view showing a flow of an query messageencrypting processing in a secure multi-database system according to oneembodiment of the present invention.

FIG. 12 is an explanatory view showing a flow of an MDB querydecomposition processing in a secure multi-database system according toone embodiment of the present invention.

FIG. 13 is an explanatory view showing a flow of an query messagedecrypting processing in a secure multi-database system according to oneembodiment of the present invention.

FIG. 14 is an explanatory view showing a flow of a result tableencrypting processing in a secure multi-database system according to oneembodiment of the present invention.

FIG. 15 is an explanatory view showing a flow of an MDB result tableintegration processing in a secure multi-database system according toone embodiment of the present invention.

FIG. 16 is an explanatory view showing a flow of a result tabledecrypting processing in a secure multi-database system according to oneembodiment of the present invention.

FIG. 17 is an explanatory view showing an entire configuration of aninformation mediation system according to one embodiment of the presentinvention.

DETAILED DESCRIPTION

First of all, a schematic configuration of an embodiment of the presentinvention is explained. A secure multi-database system according to thepresent invention includes a multi-database definition tool, amulti-database server, at least one client program and an at least oneexternal database server.

Then, means which is employed at the time of defining the multi-databasesystem is explained.

The multi-database definition tool declares columns which areconfidential to the multi-database server (concealment columns) out ofan external table and registers information on these concealment columnsinto a dictionary of the multi-database server. Further, themulti-database server controls the definition of a view table and theregistration of the definition into the dictionary such that when a userdefines the view table using the concealment columns, an arithmeticusing the concealment columns is not performed. In this specification,“concealment” includes the alteration of the column into other dataform. Further, “concealment” may mean to control the disclosure of thecontent such as encrypting.

Subsequently, means used at the time of executing the multi-databasesystem is explained.

The multi-database server controls the decomposition and execution ofthe query messages such that when the users executes the query messagesincluding the concealment columns, the user does not perform thearithmetic using the concealment columns. An external database serverexecutes respective query messages and generates a result table.Further, the external database server encrypts data in the concealmentcolumn before returning the result table to the multi-database server.The multi-database server preliminarily sets the query messages suchthat the arithmetic using concealment columns is not performed so thatresult tables can be integrated without any problems. Further, forintegrating the result tables, a range decrypted by a client program isdesignated. The client program obtains the integrated result tables andperforms decryption within a designated range. Since the data encryptedby the external database server is decrypted by the client program andis referred, it is difficult for the multi-database server to refer tothe content of the concealment columns.

Subsequently, a manner for concealing a portion of the query messagesfrom the multi-database server is explained. First of all, the clientprogram designates a range to be encrypted within the query messages.Then, after executing this encrypting, the client program transmits thequery messages including the encrypting range to the multi-databaseserver. In the same manner as the previously mentioned processing, themulti-database server performs the decomposition and the execution ofthe query messages such that the arithmetic related with this encryptingrange can not be executed. The external database server extracts anddecrypts the encrypted range in the query messages before executingrespective query messages.

Subsequently, means to solve tasks in the information mediation systemis explained.

The information mediation system is comprised of a mediator, at leastone user and at least one information provider. The informationproviders declare a concealment range to the mediator. The mediatorcontrols the decomposition and the execution of query messages such thatwhen the user executes the query messages contained in the concealmentrange, the arithmetic using the concealment range is not performed. Theinformation provider executes respective query messages and producesresult tables. Further, the information provider encrypts data withinthe concealment range before returning the result tables to themediator. Since the mediator preliminarily sets the query messages suchthat the arithmetic using the concealment range is not performed, themediator can integrate the result tables without any problems.

Further, for integrating the result tables, the mediator designates arange decrypted by the user. The user acquires the integrated resulttables and decrypts the designated range. Since the data encrypted atthe information provider side is decrypted and is referred at the userside, it is difficult for the mediator to refer to the content of theconcealment range.

The same goes for a method which conceals a portion of the querymessages to the mediator. First of all, the user designates a range tobe encrypted in the query messages. Then, after executing thisencryption, the user transmits the query messages containing theencrypted range to the mediator. In the same manner as theabove-mentioned processing, the mediator controls the decomposition andexecution of the query messages such that the arithmetic related withthis encrypting range is not executed. The information provider extractsthe encrypting range in the query messages before executing respectivequery messages and decrypts them.

The detail of the embodiment is explained hereinafter. First of all, thefirst embodiment of the present invention is explained hereinafter inconjunction with drawings.

FIG. 1 is an explanatory view showing a software configuration of asecure multi-database system according to one embodiment of the presentinvention. The secure multi-database system includes a multi-databaseserver 1, a multi-database definition tool 2 (MDB definition tool), aclient program 3 and an external database server 4. Although only oneclient program is described in FIG. 1, it is possible to get access tothe multi-database server from a plurality of client programs. Further,as shown in FIG. 1, the multi-database server can get access to aplurality of external database servers.

Hereinafter, the configurations of respective software are explainedfocusing on the features of the present invention.

First of all, the multi-database definition tool 2 preparesmulti-database definition messages (MDB definition message) 20 andregisters these definition messages 20 to the multi-database server 1through a multi-database interface part (MDB interface part) 33. As themulti-database definition messages 20, definitions of an external datawrapper, an external table and a viewer table and the like are named.The present invention is characterized in that when the external DBincludes columns to be concealed from the multi-database server(concealment columns), this columns are declared by the MDB definitionmessages.

Then, the client program 3 prepares query messages to the multi-database(MDB query messages) 30 and encrypts a portion of this query messages 30in an query message encrypting processing 32 and transmits the querymessages 30 to the multi-database server through the MDB interface part33. Here, the present invention is characterized in that in the MDBquery messages 30, the range to be encrypted can be designated(encrypting designation 31), and the encryption is executed based onthis encrypting designation 31 in the query encrypting processing 32.Accordingly, a portion of the encrypted messages is included in MDBquery messages 50 transmitted to the multi-database server 1.

Further, the client program 3 acquires a result table (MDB result table)53 of the multi-database including the encrypted messages through theMDB interface part 33 and a portion of the result table 53 is decryptedin the result table decrypting processing 34. Here, since a range to bedecrypted is designated in the MDB result table 53, the result tabledecrypting processing 34 is characterized in that the decrypting isperformed based on such a decrypting designation. Accordingly, the MDBresult table 35 used in the client program becomes the plain message.

Subsequently, the multi-database server 1 is provided with amulti-database definition registration processing (MDB definitionregistration processing) 15 and registers the MDB definition message 20from the MDB definition tool 2 to a dictionary in the inside DB 17thereof. Here, when the concealment column declaration 21 is containedin the MDB definition message 20, this concealment column declaration 21is registered in the dictionary as the concealment column information18. The present invention is characterized in that the registration ofMDB definition message is controlled by referring to the concealmentcolumn information 18 in the MDB definition registration processing 15.Here, “control” means to suppress the registration of MDB definitionmessage into the dictionary when there exists the MDB definition messagewhich performs the arithmetic using the concealment column in themulti-database server 1. If this registration is freely allowed, sincethe multi-database server 1 is not informed of the data value ofconcealment column, an unexpected arithmetic effect may be broughtabout.

Further, the multi-database server 1 acquires the MDB query message 50including the encrypted message from the client program 3 and decomposesthis MDB query message 50 into query messages (external DB querymessages) 51 for every external database server in the MDB query messagedecomposition processing 10 and supplies them to the external databaseserver 4 through the external DB interface part 12. Here, the externalDB interface part 12 corresponds to an external data wrapper. Thepresent invention is characterized in that the decomposition andexecution of the MDB query message 50 are controlled by referring to theencrypting designation 30 and the concealment column information 18 inthe MDB query message decomposition processing 10. Here, “control”means, for example, to suppress the execution of this MDB query messagewhen there exists the MDB query message which allows the arithmeticusing the concealment column to be performed in the multi-databaseserver 1. In the same manner, when there exists the MDB query messagewhich allows the execution of the arithmetic using the encryptiondesignated data value in the multi-database server 1, the execution ofthis MDB query is suppressed. If this execution is freely allowed, sincethe multi-database server 1 is not informed of the data value of theconcealment column and the encryption designated data value, there is apossibility that an unexpected arithmetic result is brought about.

Further, the present invention is also characterized in that the MDBquery message 50 is decomposed into the external DB query messages 51having the configuration which includes the encrypting designation 31.Accordingly, the external DB query messages 51 to be transmitted to theexternal database server 4 includes the encrypting designation 31together with a partial encrypting message.

Further, the multi-database server 1 acquires the external DB resulttables 52 including encrypted message from respective external databaseservers 4, integrates this external DB result tables 52 at the MDBresult table integrating processing 13 and transmits the result table 52to the client program 3. The present invention is characterized in thatthe range to be decrypted in the client programs 3 is designated in theMDB result table integrating processing 13. Accordingly, the MDB resulttable 53 transmitted to the client program includes the decryptingdesignation 14 along with partial encrypting message.

Subsequently, the external database server 4 acquires the external DBquery message 51 including the encrypted message and this external DBquery message 51 is decrypted by the query message decrypting processing40 and the external DB query message 41 which is generated by such adecryption and is all made of plain message is transmitted to theDBMS42. The present invention is characterized in that the decryption isperformed in accordance with the encrypting designation 31 in the querymessage decrypting processing 40.

Further, the DBMS 42 generates the external DB result table 43 afterexecuting the query. Although the external DB result table 43 is allformed of plain message, the result table decrypting processing 44encrypts a portion of the result table by referring to information 46 onthe concealment column preliminarily registered in the dictionary of theexternal DB 45 and thereafter transmits the encrypted result table tothe multi-database server 1 as the external DB result table.Accordingly, the external DB result table partially includes theencrypted message.

In FIG. 1, the concealment column information 18 is disposed in theinternal DB 17 of the multi-database server 1 and the concealment columninformation 46 is disposed at the external DB 45 of the externaldatabase server 4. The concealment column information 18 is informationrelating to the concealment column in a range declared as the externaltable in the multi-database server 1. On the other hand, the concealmentcolumn information 46 is information relating to the concealment columnincluded in the external database server 4. The definition andregistration of the concealment column information 46 are performed bythe external database definition tool or the like not shown in thedrawing. Further, in the previously mentioned multi-database definitiontool 2, to ensure the consistency with the external database, it isdesirable to adopt a mode in which the concealment column is declared byreferring to the concealment column information 46. Alternatively, it ispreferable to adopt a mode in which the concealment column information18 is automatically determined based on the concealment columninformation 46 in a range declared as the external table in themulti-database server 1. Although it may be possible to adopt a mode inwhich the concealment column of the external database is declared by themulti-database definition tool 2, this becomes a mode in which thedeclaration is transmitted to the external database server 4 through themulti-database server 1 and hence, this mode is liable to induce animproper processing in the multi-database server 1. Accordingly, it isone of the features of the present invention that the concealment columnis declared first at the external database and thereafter theconcealment column is declared at the multi-database by reference to theconcealment column.

Here, the encrypting system and the decrypting method are explained.

In this embodiment, it is a presumption that the client program 3 andthe external database server 4 know the encrypting and decrypting methodof the counterpart each other. This is because that it is necessary toperform the decrypting in conformity with the encrypting method of thecounterpart.

The first embodiment having the simplest configuration is to integratethe encrypting method and the decrypting method in the multi-databasesystem as a whole. To be more specific, encrypting and decryptingalgorithms which are common in respective client programs 3 and theexternal database server 4 are mounted by a plug-in connection. Thisembodiment is explained in detail based on this method. The exchange ofthe key for the encrypting and the decrypting is explained hereinafter.

The second embodiment relates to a case in which an encrypting functionis added to an existing external database server 4. In this case,although it is necessary for the client program 3 to specify a resulttable which is acquired from respective external database servers 4,this operation can be performed by the decrypting designation 14. Sincethe name of the external database server 4 in which the result table isprepared is described in the decrypting designation 14, the decryptingmethod can be specified based on this. In this case, it is necessary forthe client program 3 to preliminarily know the decrypting method forevery external database server 4.

Further, in transmitting the query message including the encryptingrange from the client program 3 to the external database server 4, it isnecessary to specify the external database server 4 to which theencrypting range is transmitted by the client program 3. In this case,it is necessary to preliminarily make an query to the multi-databaseserver 1 with respect to the external database server 4 to which thequery message is transmitted. Once the destination to which theencrypting range is transmitted is found, the range is encrypted inconformity with the decrypting system of the counterpart.

The exchange of key in the second embodiment is substantially as same asthe exchange of key of the first embodiment which will be explainedhereinafter.

The exchange of key for encryption and decryption is explainedhereinafter.

First of all, in this embodiment, two kinds of keys are used, whereinone key is used for encrypting and decrypting the query message and theother key is used for encrypting and decrypting of the result table.Assume a common key encrypting method which uses a same key forencrypting and decrypting. The common key for query message istransmitted from respective client programs 3 to the external databaseserver 4. Further, the common key for result table is transmitted fromrespective external database servers 4 to the client program 3.

The simplest embodiment is a case in which the exchange of these commonkeys is performed by means such as letters, telephones or the likewithout using a network before the query is made. It is necessary thatthe registration of these common keys to the client programs 3 and theexternal database servers 4 is safely performed manually. Further, atthe time of executing the encrypting or the decrypting, the common keysare specified by a user authentication.

To perform the exchange of key through the network without a manualoperation, it is necessary to prevent the common keys from being stolenon the network. An open key encrypting method is used to satisfy thisrequisite. With respect to the common key for query message, the clientprogram 3 performs the encrypting using open keys of respective externaldatabase servers 4 and transmits the encrypted query message to theexternal database server 4. In the external database server 4, theexternal database 4 decrypts this encrypted message using its own secretkey and obtains the common key. On the other hand, with respect to thecommon key for result table, respective external data base servers 4encrypt the result table using the open key of the client program 3 andtransmit this encrypted result table to the client program 3. In theclient program 3, the client program 3 decrypts this encrypted resulttable using its own secret key and can obtain the common key. When theopen key can be obtained from each other, the security is furtherenhanced by positively making use of an authentication bureau or thelike so as to obtain the open keys with certificates.

When the connection is established from the client program 3 to themulti-database server 1, the user authentication is performed. An accesscontrol to the multi-database is performed based on the userauthentication. The security is further enhanced by combining thepresent invention, the user authentication and the access control, forexample, by allowing only a proprietor of the table containing thecolumn to perform the declaration of the concealment column. Further, itis needless to say that the query to the table to which the user has noprivilege to access is suppressed by the multi-database server.

Also at the time of establishing the connection from the multi-databaseserver 1 to the external database server 4, the user authentication isperformed. An access control to the external database is performed basedon the user authentication. The security is further enhanced bycombining the present invention, the user authentication and the accesscontrol, for example, by allowing the concealment column information 46to open to only a proprietor of the table containing the column.

FIG. 2 is an explanatory view showing a hardware configuration of asecure multi-database system according to one embodiment of the presentinvention. The secure multi-database system includes computers 61-65which are respectively connected with each other through a network 60and respective software which are explained in FIG. 1 are arranged inrespective computers. Although respective softwares are arranged inrespective individual computers in the drawing, a plurality of softwaresmay be arranged in the same computer. Further, although only one clientprogram and two external database servers are described in the drawing,it may be possible to provide a configuration which includes more clientprograms and external database servers. Assuming an application modeshown in FIG. 17, the network 60 becomes a WAN (Wide Area Network).However, the present invention is applicable to a LAN (Local AreaNetwork) in the same manner. As shown in the drawing, each computerincludes a processing device (processor) such as a CPU, a memory, astorage device which stores a program, an interface which performs atransmission/reception of information between the computer and thenetwork and paths which connect them. Further, each computer may beprovided with an output device such as a display device including adisplay and an input device such as a keyboard, a mouse or the likewhich accepts an input from a user. Further, an MDB definition tool 2and a client program 3 may be provided to the same computer.

FIG. 3 is an explanatory view showing an application example of thesecure multi-database system according to one embodiment of the presentinvention. Further, FIG. 4 to FIG. 8 describe contents related with thisapplication example. The contents of the application example areexplained hereinafter.

First of all, as the external databases, an A company data base 4(database name being A_DB) and a B company data base 5 (database namebeing B_DB) are provided. Respective databases hold a table 90 (tablename being A1) and a table 95 (table name being B1) relating to thetransaction information. Further, respective table have the equalconfiguration and each table includes a date column 91, a sales companyname column 92, a client name column 93 and a transaction amount column94.

Subsequently, the multi-database server 1 declares the tables 90, 95 asthe external tables and a view table 80 (table name being aaa1) wherethe client name is aaa company is defined. Here, the view table 80 is avirtual detailed slip in which the transaction details extending oversales companies A and B are merged exclusively with respect to theclient aaa. The view table is constituted by a date column 81, a salescompany name column 82 and a transaction amount column 83. Here, sincethe data in the transaction amount column 83 is confidential informationnot only for the client but also for the sales company, it must beconcealed from the multi-database server. In this example, it is assumedthat a range 84 is encrypted (that is, concealed).

Then, in the client program 3, the encrypted range 84 in the view table80 is decrypted and a view table 70 in which all data are in plainmessages is provided.

FIG. 4 and FIG. 5 show an example of a multi-database definition message20.

First of all, FIG. 4 is an explanatory view showing an example of adefinition message 99 of the external table in the secure multi-databasesystem according to one embodiment of the present invention. To be morespecific, FIG. 4 shows the definition message for registering the tables90, 95 described in FIG. 3 in the multi-database server. In thisembodiment, a declarator 21 which is called ENCRYPTED is used. Theinvention is characterized in that the external database server declaresa column which is concealed from the multi-database server. Here, theconcealment column information 46 preliminarily defined in the externaldatabase is referred.

Subsequently, FIG. 5 is an explanatory view showing an example of adefinition message 100 of the view table in the secure multi-databasesystem according to one embodiment of the present invention. To be morespecific, FIG. 5 shows the definition message for registering the viewtable 80 described in FIG. 3 in the multi-database server. As shown inthis example with respect to the table of the external database which isdeclared as the external table, the view can be defined in the samemanner as an internal table.

Further, although not shown in the drawing, a definition message whichregisters the external database server and a definition message whichchanges or deletes definition information registered in themulti-database server are present.

FIG. 6 is an explanatory view showing a processing flow of an querymessage in the secure multi-database system according to the presentinvention using an application example.

First of all, in the client program 3, an MDB query message 30 whichselects records of transaction amount of not less than 750000 from aview table la is generated. The present invention is characterized inthat, in the client program 3, a range encrypted in the MDB querymessage 30 is designated to the multi-database server 1 using adeclarator 31 called ENCRYPT. The encrypting range surrounded by theENCRYPT declarator is usually a constant in retrieval conditions.

In the query encrypting processing 32, this ENCRYPT declarator 31 isextracted and the encrypting range is specified. In the MDB querymessage 50, a constant surrounded by the ENCRYPTED declarator 55indicates the encrypted range. Here, the reason for using the ENCRYPTdeclarator 31 and the ENCRYPTED declarator 55 separately is that theprogram can classify the range to be encrypted and the range to bedecrypted.

Subsequently, in the multi-database server 1, the MDB querydecomposition processing 10 decomposes the MDB query message 50 intoindividual query messages 51 a, 51 b which are transmitted to therespective external database servers. In the drawing, the column nameand the table name are specified and a condition to retrieve recordshaving the client name of aaa is added. Further, in the retrievalcondition relating to the transaction amount, an ENCRYPTED declarator 56is used as in the case of the MDB query message.

Then, in the external databases 4 and 5, the query decrypting processing40 a and 40 b extract the ENCRYPTED declarator 56 and decrypt theconstant surrounded by the declarator 56. As a result, a constant 48indicative of 750000 is acquired and an query message 41 which can beprocessed at each DBS42 can be generated.

Besides the SELECT message, an INSERT message, a DELETE message and anUPDATE message are processed in accordance with a similar flow ofprocessing. Particularly, with respect to the INSERT message and theUPDATE message, not only the constant in the retrieval conditions butalso data values to be inserted or updated are encrypted. Due to such amethod, the present invention is characterized in that the contentswhich are added or updated in the external databases can be concealedfrom the multi-database server 1 in view of an application example.

FIG. 7 is an explanatory view showing a processing flow of the resulttable in the secure multi-database system according to one embodiment ofthe present invention. FIG. 7 shows a result to the query of FIG. 6.

First of all, in the external databases 4 and 5, result table encryptingprocessing 44 a, 44 b encrypt data values of concealment columns of theexternal DB result tables 43 which are results of execution atrespective DBMS 42. In this example, the transaction amount columns 123become the concealment columns. Accordingly, as shown in the external DBresult tables 52 a, 52 b, the data values of the transaction amountcolumns 113 are encrypted so that they cannot be referred from othermeans. Further, the present invention is characterized in that ENCRYPTEDcolumns 114 (column name being ENC1) are added to specify the range thatresult table encrypting processing 44 a, 44 b encrypt. In this example,FIG. 7 shows that the concealment columns are included in thetransaction amount columns 113 disposed at the left side of theENCRYPTED columns 114 and the range of encrypted records is indicated bythe database name in the inside of the ENCRYPTED columns 114. When thiscolumn 114 is Null, this implies that the same records in the column atthe left side of the ENCRYPTED columns 114 is not encrypted. The aboveis a processing for easily specifying the encrypted range when theconcealment column and the non-concealment column are merged. That is,the processing is provided for easily specifying the decrypted keys whendecrypted keys are different every database.

Subsequently, in the multi-database server 1, the MDB result tableintegration processing 13 integrates respective external DB resulttables 52 a and 52 b. According to the definitions of the view tabledescribed in FIG. 5, since this view table indicates the merger ofexternal tables, the processing performed at the MDB result tableintegration processing 13 becomes the merging processing of the externalDB result tables 52 a and 52 b. Here, the transaction amount column 103and the ENCRYPTED column 104 which contain the encrypted data are alsomerged so that the MDB result table 53 can be obtained.

Then, in the client program 3, the result table decrypting processing 34refers to the ENCRYPTED column 104 of the MDB result table 53 anddecrypts the data values of the transaction amount column 103 at recordshaving data values other than Null. That is, the ENCRYPTED column 104functions as decrypting designation 14. Then, an MDB result table 35formed of only plain messages is obtained.

When it is necessary to ensure the consistency of data in the inside ofthe concealment column acquired from the external database, the dataconversion is performed before performing the encrypting processing atthe external database server or after performing the decryptingprocessing at the client program.

FIG. 8 is an explanatory view showing an application example of externaltable definition information in the secure multi-database systemaccording to one embodiment of the present invention. To be morespecific, FIG. 8 shows the external table definition informationrelating to definition messages 99 of the external table described inFIG. 4. Although the present invention is similar to the conventionalmulti-database system on a point that the multi-database system includesrespective definition information consisting of a DB name 131, a tablename 132, a column name 133, a data type 134, a data length 135, anaccuracy 136, a NULLABLE 137 and the like, the present invention ischaracterized in that information relating to the concealment column ofthe external table is administrated at an ENCRYPTED column 138. Theexample shown in FIG. 8 indicates that the column name “transactionamount” is declared as the concealment column in the table name “A1” ofthe DB name “A_DB” and the column name “transaction amount” is declaredas the concealment column in the table name “B1” of the DB name “B_DB”.

FIG. 9-FIG. 16 are explanatory views showing flows of processing of thesecure multi-database system according to one embodiment of the presentinvention. Respective processing are explained hereinafter step by step.

FIG. 9 shows the flow of the MDB definition registration processing 15.First of all, in step 141, the syntactic analysis of the MDB definitionmessage to be registered is performed. Subsequently, in steps 142-143,the processing is branched for every syntactic. In FIG. 9, only the MDBdefinition registration processing relating to the features of thepresent invention is described.

In a CREATE FOREIGN TABLE message of step 142, the definition messagedescribed in FIG. 4 becomes a subject. First of all, in step 144, themeaning check of this definition message is performed. Here, the meaningcheck is a processing which checks whether the external DB quoted in thedefinition message properly exists in the inside of a dictionary or not,whether a table which has the same name has already existed or not andthe like. Subsequently, in step 145, only when the external DB properlyexists in step 144, the definition message is registered in thedictionary as the external table definition information. An ENCRYPTEDdeclarator is also neatly analyzed and a transaction amount columnsurrounded by the declarator is registered as a concealment column.

In a CREATE VIEW message of step 143, the definition message 100described in FIG. 5 becomes a subject. As in the case of the CREATEFOREIGN TABLE message, a meaning check 146 and a registration 147 in aview table definition information are performed. In the view table, whenthe concealment column of the external table is used in the querydesignation, since the multi-database server can not refer to the dataof the concealment column, there may be a case that the manipulation ofthe view table can not be performed. Accordingly, a meaning check 150 ofthe query designation by reference to the concealment column isprovided.

FIG. 10 shows the flow of processing of the meaning check 150 of thequery designation by reference to the concealment column shown in FIG.9. In step 161, the query designations corresponding to a plurality ofexternal tables on different external DB are extracted. This means thateven when one external table or a plurality of external tables areprovided, so long as these external tables are disposed in the sameexternal DB, the query designations by reference to the concealmentcolumn can be directly transmitted to the external DB and processedthere without any problems. Here, a problem that an accurate arithmeticcan not be performed properly when the query designation by reference tothe concealment column is transmitted over a plurality of external DBscan be solved.

Then, in step 162, the query designation in which the concealmentcolumns are present in respective clauses other than a SELECT clause isextracted. Subsequently, in step 163, the query designation in which itis necessary to perform an arithmetic using the concealment column inthe multi-database server is extracted.

As an example which performs an arithmetic using the concealment column,a case in which the concealment column is used as a coupling conditionin the query message which couples the external tables, a case in which,in a sub-query including the external table, a result of the sub-querybecomes the concealment column, a case in which the concealment columnis used as a GROUP BY clause or a ORDER BY clause in an query messagewhich performs a set arithmetic of the external tables, a case in whicha set difference or a set product is performed against external tableincluding the concealment columns and the like are considered.

There may be a case that even an arithmetic using the concealment columncan be properly processed using the multi-database server 1. Forexample, depending on the encrypting method (the encrypting method whichdirectly follows the mathematical characteristics of plain messages),the comparison of the magnitude, the equivalence and the like can beperformed such as a case which compares both concealment columns.Particularly, when the same encrypting key is used, the comparison ofequivalence of the concealment columns can be performed. In such a case,a mode which becomes an exception of step 163 may be considered.

Finally, to the query message including the query designation detectedin step 163, an error or an alarm is generated in step 164 so as tocontrol the execution of query message. With respect to other querymessages, the execution of these query messages is continued without anychange.

FIG. 11 shows the flow of query message encrypting processing 32. Firstof all, in step 171, a syntactic analysis of MDB query message isperformed. Subsequently, in step 172, constants in the inside of the MDBquery message are acquired. If the designation by the ENCRYPT declaratoris provided to the constants, the constants are encrypted in step 174.Steps 172-174 are executed with respect to all constants in the MDBquery message.

Although the mode in which the ENCRYPT declarator is designated to theconstants is adopted in this embodiment, the same flow of processingshown in FIG. 11 is executed when the ENCRYPT declarator is designatedto other items.

FIG. 12 shows the flow of query message decomposition processing 10.First of all, in step 181, a syntactic analysis of the MDB query messageis performed. Subsequently, in step 182, as in the case of thepreviously mentioned view table definition, when the concealment columnof the external table is used in the query designation, since themulti-database server can not refer to the data of the concealmentcolumn, there may be a case that MDB query message can not be executed.Accordingly, the meaning check 150 of the query designation by referringto the concealment column is performed and the execution of the MDBquery message is controlled. Subsequently, in step 184, an access pathat the time of decomposing the MDB query message is optimized. Here, thecontrol is performed such that the path which does not perform thearithmetic using the concealment column in the multi-database server isselected. For example, with respect to the query message which includesthe sub-query, to enhance the performance, the path in which the mainquery message and the sub-query message are processed by respectiveexternal DBs in parallel and respective results are again processed bymulti-database server is considered. However, when the main querymessage includes the concealment column and the sub-query message doesnot include the concealment column, a path which transmits the result ofthe sub-query message along with the main query message to the externalDB is selected. Finally, in step 186, the query message for everyexternal DB is generated.

The present invention is characterized in that at the time ofdecomposing the MDB query message into the query messages of respectiveexternal DBs, a control is performed such that an arithmetic using theconcealment column is not executed by the multi-database server. As aresult, the multi-database server can integrate the external resulttables even when the multi-database server is not informed of thecontent of the concealment column without any problems.

FIG. 13 shows the flow of query decrypting processing 40. First of all,in step 191, a syntactic analysis of the external DB query message isperformed. Subsequently, constants in the inside of the external DBquery message can be obtained in step 192. Then, in step 193, when thedesignation by the ENCRYPTED declarator is provided to the constants,the constants are decrypted in step 194. The steps 192-194 are executedto all constants in the inside of the external DB query message.

Although a mode in which the ENCRYPTED declarator is designated to theconstants is adopted, even when the ENCRYPTED declarator is designatedto other items, the same processing flow shown in FIG. 13 can beexecuted.

FIG. 14 shows the flow of result table decrypting processing 44. Firstof all, in step 201, information of the concealment column is acquired.Following steps 202-206 are processing which are executed to all columnsof the external DB result table. In step 202, the columns of theexternal DB result table are acquired. In step 203, whether the columnis the concealment column or not is judged. If the column is theconcealment column, data of all records of the column are encrypted instep 204. Then, in step 205, an ENCRYPTED column is added to the rightside of the column. In step 206, to indicate that the data of theconcealment column has been encrypted, data of the ENCRYPTED column areset in a database name. As mentioned previously, since the steps 202-206are processing executed to all columns of the external DB result table,it is judged whether other columns remain in step 207 or not.

FIG. 15 shows the flow of the processing of the MDB result tableintegration processing 13. First of all, in step 211, a framework of theMDB result table is prepared in accordance with the result of the MDBquery message decomposition processing 10. Subsequently, in step 212,the external DB result tables are acquired from respective external DBs.Then, in step 213, it is judged whether the ENCRYPTED columns arepresent in the external DB result tables or not. If the ENCRYPTEDcolumns are not present, the external DB result tables are inserted intothe MDB result table in accordance with the framework. If the ENCRYPTEDcolumns are present, in step 214, the ENCRYPTED columns are added to theframework of the MDB result table. Then, in step 215, the external DBresult tables are inserted into the MDB result table in a form that theENCRYPTED columns are included in the external DB result table. Theabove-mentioned processing of steps 212-216 are executed to all externalDB result tables acquired by the multi-database server. In step 217, thejudgment to this end is executed. Finally, in step 218, empty recordsare all set to Null in the ENCRYPTED columns. The above is a processingperformed at the time of integrating the external DB result tables whichdo not have the ENCRYPTED columns and the external DB result tableswhich have the ENCRYPTED columns.

FIG. 16 shows the flow of the result table decrypting processing 34.First of all, in step 231, the columns of MDB result tables areobtained. Subsequently, in step 232, it is judged whether the columnsare ENCRYPTED columns or not. When the columns are the ENCRYPTEDcolumns, the processing of steps 233-238 are executed. When the columnsare not ENCRYPTED columns, the processing advances to step 239. In step233, the columns disposed at the left side of the columns are acquired.According to the processing which have been explained heretofore, theencrypted data should be included in the column disposed at the leftside of the column. In step 234, the record values of the ENCRYPTEDcolumns are acquired. In step 235, it is judged whether the recordvalues are database names or Null. When the record values are databasenames, following steps 236-237 are repeated. When the record values areNull, the processing advances to step 238. In step 236, the recordvalues of the column disposed at the left side of the column areacquired. Since it is assumed that the record values are encrypted instep 237, these record values are decrypted. In this case, sincedecrypting keys are different every database, the database names aregiven to keys. In step 238, it is judged whether other records arepresent or not and when the other records are present, steps 234-237 arerepeated. Further, in step 239, it is judged whether columns of otherMDB result tables are present or not and when the columns are present,steps 231-238 are repeated.

FIG. 17 is an explanatory view showing the configuration of aninformation mediation system according to the second embodiment of thepresent invention.

The information mediation system virtually integrates informationsources which are distributed on a network and provides an unitaryaccess path to users. Since the designations to which inquiries are madecan be arranged in one, when viewed from the users, an advantageouseffect that the availability of the system is increased can be obtained.

In FIG. 17, a mediator 301 provides an access path to a sales company A304 a, a sales company B 304 b and a sales company C 304 c as virtualdetailed statement slip 302 a-302 c to an aaa company 303 a, a bbbcompany 303 b and a ccc company 303 c which constitute cliententerprises. The substance of the virtual detailed statement slips is aview table which declares transaction information 45 a, 45 b and 45 c asexternal tables in a multi-database server 1 and merges respectiveclient enterprises into a key. Inquiries from clients 3 a, 3 b, 3 c aretransmitted to respective DB 45 a-45 c through the multi-database server1 and the query result tables (result tables) are integrated andreturned to respective clients.

A method for concealing contents of the virtual detailed statement slipstransacted between the client enterprises 303 and the sales companies304 from a mediator 301 is as follows.

First of all, the sales companies 304 declare a range to be concealedagainst the mediator 301. The mediator 301 controls the decompositionand the execution of query messages such that the client enterprises 303do not perform an arithmetic using the concealed range at the time ofexecuting the query messages including the concealed range. The salescompanies 304 execute respective query messages and generate individualdetailed statement slips. Further, the sales companies encrypt datawithin the concealed range before returning the detailed statement slipsto the mediator 301. Since the query messages are preliminary set suchthat the arithmetic using the concealed range can not be performed, themediator 301 can integrate the detailed statement slips without anyproblems. Further, in integrating the detailed statement slips, therange to be decrypted is designated in the client enterprises 303. Theclient enterprises 303 acquire the integrated detailed statement slips,that is, virtual detailed statement slips and decrypt the designatedrange. Since the data encrypted at the sales company 304 side aredecrypted and referred at the client enterprises 303 side, it isdifficult for the mediator to refer to the contents of the concealedrange.

Then, a method which conceals a portion of query messages against themediator 301 is explained. First of all, the client enterprise 303designates a range to be encrypted within the query message. Then, afterexecuting this encrypting, the query message containing the encryptedrange is transmitted to the mediator 301.

In the same manner as the previous case, the mediator 301 controls thedecomposition and the execution of the query message such that anarithmetic relating to this encrypted range is not executed. The salescompany 304 extracts the encrypted range within the query message beforeexecuting respective query messages and decrypts them.

Although the example in which the information mediation system isapplied to the B2B-type mode has been explained in this embodiment, theinformation mediation system can be applied to a B2C-type mode. To bemore specific, a service which integrates electronic detailed statementslips held by financial institutions such as a credit company or a loancompany with respect to every individual and provides them to users, ora service which integrates electronic medical reports held by respectivemedical institutions with respect to every individual and provides themto users and the like are considered.

According to the present invention, the secure multi-database system inwhich even the administrator cannot easily look into the contents of thedata transacted between the client and the external data base can berealized. By allowing the client or the external database system todeclare the range to be concealed from the multi-database system, theoperation of the multi-database system which takes a trade-off betweenthe security and the manipulation of the database into account becomespossible compared with a prior art which conceals the whole range.

Further, the information mediation system which make it difficult foreven an administrator to look into the contents of informationtransacted between the users and the information providers can berealized. Since the reliability can be easily obtained from the usersand the information providers with the use of this system, the businessof the information mediation service can be smoothly promoted.

What is claimed is:
 1. A multi-database system comprising: a pluralityof database devices for storing distributed data; a multi-databaseprocessing device coupled to the plurality of database devices over anetwork to receive the distributed data and perform an integrationprocess on the distributed data, the integration process generatingintegrally processed data; and a user processing device coupled to themulti-database system over the network, the user processing devicereceiving said integrally processed data from said multi-databaseprocessing device, wherein a partial data in a first data regionincluded in said distributed data is subjected to a conversionprocessing based on a preliminarily rule, wherein the user processingdevice generates a first query request including first information forindicating an area of the partial data, and sends the first queryrequest to the multi-database processing device, wherein themulti-database processing device receives the first query request fromthe user processing device, generates a plurality of second queryrequests, some of which include the first information, for the pluralityof database devices based on the first query request, and sends theplurality of second query requests to the plurality of database devices,wherein each of the plurality of database devices receives one of theplurality of second query requests, selects data requested by the one ofthe plurality of second query requests, converts the selected data andadds second information, which indicates that the selected data isconverted if the selected data are included in the partial dataindicated by the first information included in the one of the pluralityof second query requests and sends the selected data to themulti-database processing device, wherein the multi-database processingdevice receives a plurality of the selected data from the plurality ofdatabase devices, integrates the plurality of the selected data intointegrally processed data and sends the integrally processed data to theuser processing device, and wherein the user processing device receivesthe integrally processed data from the multi-database processing device,checks whether the integrally processed data includes the partial databased on the second information and re-converts the partial data ifincluded.
 2. The multi-database system of claim 1, wherein the userprocessing device converts data included in the first query request andsends the first query request which includes the converted data to themulti-database processing device, wherein the multi-database processingdevice embeds the converted data into some of the plurality of secondquery requests, wherein some of the plurality of database devices whichreceives one of the some of the plurality of second query requestsde-converts the converted data and selects data requested by theplurality of second query requests based on the de-converted data. 3.The multi-database system of claim 2, wherein said conversion processingis an encrypting processing and said re-conversion processing is adecrypting processing corresponding to said encrypting processing. 4.The multi-database system of claim 1, further comprising amulti-database definition device coupled to said multi-databaseprocessing device through the network, wherein said multi-databasedefinition device transmits definition information which defines saidfirst information to said multi-database processing device.
 5. Themulti-database system of claim 4, wherein said multi-database definitiondevice and said user device are physically integrally formed.
 6. Themulti-database system of claim 1, wherein the multi-database processingdevice generates the plurality of second query requests by performing asyntactic analysis of the first query request, interpreting the firstquery request using a concealment column, and selecting a path that doesnot perform an arithmetic operation using the concealment column.
 7. Themulti-database system of claim 1, wherein the multi-database processingdevice integrates the plurality of the selected data into integrallyprocessed data by preparing a framework of a first result table,obtaining second result tables from remote databases, determiningwhether or not an encrypted column is present in the second resulttables, adding the encrypted column to the framework of the first resulttable if the encrypted column is present in the second result tables,and inserting the external results tables including the encrypted columnto the first result table.
 8. The multi-database system of claim 1,wherein the user processing device re-converts the partial data byobtaining columns of a first result table, determining whether or notone or more the columns of the table are encrypted, retrieving anencrypted column if the table includes one or more encrypted columns,obtaining a record value of the retrieved encrypted column, anddecrypting the obtained record value.
 9. A multi-database processingdevice comprising: a path, an interface part coupled to said path and toa network; a storage device coupled to said path, the storage devicestoring a program for performing an integration processing operation,and a processing device coupled to said interface part and said storagedevice through said path, the processing device executing the program toperform the integration processing operation on distributed datareceived at said interface part from a plurality of database devices,wherein said storage device receives a plurality of distributed datathat are obtained by applying a conversion processing operation to apartial data in a first data region in said distributed data based on apreliminarily determined rule, and said processing device generatesintegrated data, in accordance with said integration processingoperation, by integrating a plurality of said received distributed databased on said program and transmits said integrated data from saidinterface part to a user device, wherein the multi-database processingdevice receives a first query request from the user device coupled tothe multi-database processing device, the first query request includingfirst information indicating the first data region associated with thepartial data, wherein the multi-database processing device generates aplurality of second query requests, some of which include the firstinformation and some of which does not include the first information,for the plurality of database devices based on the first query request,and sends the plurality of second query requests to the plurality ofdatabase devices, wherein each of the plurality of database devicesreceives one of the plurality of second query requests, selects datarequested by the one of the plurality of second query requests, convertsthe selected data and adds second information if the selected data areassociated with first data region indicated by the first information andsends the selected data to the multi-database processing device, andwherein the multi-database processing device receives a plurality of theselected data from the plurality of database devices, integrates theplurality of the selected data into integrally processed data and sendsthe integrally processed data to the user device.
 10. The multi-databaseprocessing device of claim 9, wherein said conversion processingoperation is an encrypting processing operation.
 11. The multi-databaseprocessing device of claim 9, wherein said interface part is coupled toa multi-database definition device through the network and receivesdefinition information which defines said first information transmittedfrom said multi-database definition device.
 12. A user processing devicein which a plurality of database devices which respectively store dataand a multi-database processing device which performs an integrationprocessing on data stored in a plurality of said database devices areconnected through a network and said user processing device receivesdata which is subjected to said integration processing from saidmulti-database processing device, said user processing devicecomprising: means for receiving integrated data which saidmulti-database processing device integrates, said integrated datagenerated by integrating a plurality of distributed data wherein amongdistributed data necessary for an integration processing by saidmulti-database processing device, a conversion processing is applied toa partial data in a given data region included in said distributed databased on preliminarily determined rule at a plurality of said databasedevices; means for applying a re-conversion processing which has aprocessing content corresponding to said conversion processing topartial integrated data corresponding to the partial data to which saidconversion processing is applied among said received integrated data;and means for outputting integrated data including said partialintegrated data to which said re-conversion processing is applied,wherein the integrated data is received at the user processing device inresponse to a first query request transmitted to the multi-databaseprocessing device by the user processing device, the first query requestincluding first information identifying an area, wherein a plurality ofsecond query requests is generated at the multi-database processingdevice in response to the first query request, at least one of whichincludes area information corresponding to the first information,wherein the plurality of second query requests are transmitted to theplurality of database devices, wherein each of the plurality of databasedevices receives one of the plurality of second query requests, selectsdata requested by the one of the plurality of second query requests,converts the selected data and adds second information, which indicatesthat the selected data is converted if the selected data corresponds tothe area information included in the at least one of the plurality ofsecond query requests, wherein a plurality of the selected data from theplurality of database devices is received at the multi-databaseprocessing device, and wherein the plurality of the selected data istransformed at the multi-database processing device into integrated datato be transmitted to the user device in response to the first queryrequest.
 13. The user processing device of claim 12, wherein saidconversion processing is an encrypting processing and said re-conversionprocessing is a decrypting processing corresponding to said encryptingprocessing.